Objeitives. The surgical mortality of congenital heart defects has been reduced (or the very young age group. Especially, young age at repair is an important risk factor for mortality after repair of tetralogy of Falloff. Some risk factors were analyzed Methods. Three hundred and sixty six patients underwent surgical Intervention. Ages ranged from 5 days to 64 years, and 80 patients were adults(over 15 years of age). The defects consisted of 313(84.2%) acyanotic and 53(15.8%) cyanotic anomalies. The surgical mortalities were evaluated by univariate and multivariate analysis. Results. The overall surgical mortality was 10.4%. Mos deaths occurred in the infant group younger than 6 months(20/38 deaths) and in cyanotic group(21/38 deaths). Surgical infant mortality younger than 12 months was 24.8%(25/101). Risk factors of mortality in open heart surgery were age(p< 0.0001), body weight(p< 0.0001), pump time(p< 0.0001), aortic cross clamp time(p< 0.0001), use of total circulatory arrest(p<0.0001) and cyanotic disease(p<0.0001) by univariate analysis. But by multivariate analysis, the risk factor of mortality in open heart surgery was disease entity(p=0.002) only. A disease group with the highest risk was a cyanotic group(odds ratio was 15.3 relative to ventricular septal defect) excluding tetralogy of Falloff(odds ratio=0.27). Conclusions. Even though the most important risk factor was disease entity, we should conentrate our efforts on the technically improvable factors affecting surgical mortality indicated by univarlate analysis.